/*
 * Created on May 30, 2008
 * Created by Paul Gardner
 * 
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License only.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 */

package com.aelitis.azureus.core.util;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

public class CopyOnWriteSet<T> {
    private boolean is_identify;

    private volatile Set<T> set;

    private boolean visible = false;

    public CopyOnWriteSet(boolean identity_hash_set) {
        is_identify = identity_hash_set;

        if (is_identify) {

            set = new IdentityHashSet<T>();

        } else {

            set = new HashSet<T>();
        }
    }

    public void add(T o) {
        synchronized (this) {

            if (visible) {

                Set<T> new_set;

                if (is_identify) {

                    new_set = new IdentityHashSet<T>(set);

                } else {

                    new_set = new HashSet<T>(set);
                }

                new_set.add(o);

                set = new_set;

                visible = false;

            } else {

                set.add(o);
            }
        }
    }

    public boolean remove(T o) {
        synchronized (this) {

            if (visible) {

                Set<T> new_set;

                if (is_identify) {

                    new_set = new IdentityHashSet<T>(set);

                } else {

                    new_set = new HashSet<T>(set);
                }

                boolean res = new_set.remove(o);

                set = new_set;

                visible = false;

                return (res);

            } else {

                return (set.remove(o));
            }
        }
    }

    public boolean contains(T o) {
        return (set.contains(o));
    }

    public int size() {
        return (set.size());
    }

    public Set<T> getSet() {
        synchronized (this) {

            visible = true;

            return (set);
        }
    }

    public Iterator<T> iterator() {
        synchronized (this) {

            visible = true;

            return (new CopyOnWriteSetIterator(set.iterator()));
        }
    }

    private class CopyOnWriteSetIterator implements Iterator<T> {
        private Iterator<T> it;
        private T last;

        protected CopyOnWriteSetIterator(Iterator<T> _it) {
            it = _it;
        }

        public boolean hasNext() {
            return (it.hasNext());
        }

        public T next() {
            last = it.next();

            return (last);
        }

        public void remove() {
            // don't actually remove it from the iterator. can't go backwards with this iterator so this is
            // not a problem

            if (last == null) {

                throw (new IllegalStateException("next has not been called!"));
            }

            CopyOnWriteSet.this.remove(last);
        }
    }
}
